CSEC Biology: Seed Dispersal

The whole point of producing seeds is so that they can eventually find a suitable place to germinate and grow. As you know, seeds develop in fruits. Fruits are basically the vehicles for seed dispersal, as it is necessary for the seeds to b spread from the parent plant to give them a better chance of survival.

Why is seed dispersal important?

  • Firstly, seed dispersal prevents overcrowding. This is when plants grow too closely together and have to compete for light, water, carbon dioxide and nutrients from the soil. By spreading the seeds further apart over a larger area, this competition is avoided and the chances of survival for each seed is greatly increased.

  • Secondly, it allows for the plants to begin the colonization of new habitats. When the plants are spread out over larger areas, the chances of the survival of the species overall is increased since they can move to new habitats and gain adaptations.

The fruits of different plants have special adaptations to help dispersal.

Animal dispersal

Most succulent (fleshy) fruits contain stored food. This is attractive to animals who eat the fruit. The seeds pass through the digestive systems of these animals, and are dispersed when the animals defecate.

Some small dry fruits are adapted to have hooks that get caught on the fur of animals.

Wind Dispersal

Some smaller, dry fruits are adapted to develop wing like extensions that allow them to float by creating a larger surface area.

Other small dry fruits develop small, hair-like extensions that form a sort of parachute that provide a large enough surface area for the wind to carry the fruits or seeds.

Water Dispersal

Certain fruits will develop a waterproof exocarp, becoming buoyant, and allowing them to float on water (like coconut and manchineel)

Mechanical Dispersal

Certain dry (dehiscent) fruits split open along lines of weakness (in a sort of explosion) causing the seeds to be ejected. For example, pride of Barbados, pigeon pea and crotalaria.